I'm pretty sure they would have flown at the very least to ORD as well. They would have picked up quite a few slots from the Business Express purchase, as well as a number from TWA. Moreover, they also picked up some for American Eagle when the slot limitations for LGA were relaxed for RJ's back in 2000.

Getting Business Express away from DL and taking over their slots was a big part of the puzzle as mentioned, also the TWA takeover. They also won the slot lottery in 2000 which forced some airlines like CO to drop some routes they added like Greenville etc..